I.Causes of welding deformation
Thermal stress:During welding,the welding seam and the surrounding area expand due to the heat generated by the welding heat source,resulting in thermal stress.When welding is completed,the welding seam and the surrounding area cool down and shrink,causing the component to deform.
Temperature gradient:Different parts of the welded component experience varying degrees of heating and cooling during the welding process,creating temperature gradients.The differential shrinkage resulting from these temperature gradients leads to deformation.
Structural constraint:During welding,the welded component is constrained by the surrounding structures,preventing free shrinkage and causing welding deformation.
II.Types of welding deformation
Buckling deformation:Differential shrinkage on both sides of the welded component during cooling causes the component to bend or buckle.
Twisting deformation:The welded component experiences torque or uneven thermal stress during welding,resulting in twisting or torsional deformation along its axis.
Tensile deformation:The welded component undergoes linear elongation due to tensile stresses during welding.
Compression deformation:The welded component undergoes linear compression deformation due to compressive stresses during welding.
Thickness variation:In the welding process,the material around the welding seam and the surrounding area shrink to different extents,leading to thickness variations in the component at the weld seam.
III.Control methods for welding deformation
Optimizing welding sequence:By changing the welding sequence and positions,the temperature gradients during welding can be distributed as uniformly as possible,reducing thermal stress and deformation.
Using preheating and post-heating treatments:Preheating reduces temperature gradients and thermal stress during welding,while post-heating treatments involve uniformly heating the entire welded component to facilitate controlled cooling and minimize deformation.
Using appropriate fixtures and supports:Designing and employing suitable fixtures and supports effectively constrain the free deformation of the welded component,reducing deformation.
Controlling welding energy input:Proper control of welding energy input,including parameters such as current,voltage,and welding speed,helps minimize heat input and thermal stress,thereby reducing welding deformation.
Employing suitable welding methods:Selecting welding methods suitable for specific welding tasks,such as pulse welding or laser welding,can minimize the heat-affected zone and deformation.
Compensation welding:Allowing for certain allowances and angular deformations during the design phase enables the component to self-adjust through post-welding spring-back,achieving the desired shape and dimensions.
Using localized pre-deformation:Introducing localized pre-deformation in specific areas of the component during the design stage can compensate for deformation during the welding process,effectively controlling overall deformation.
Optimizing welding process parameters:By optimizing welding process parameters,such as pre-pressure,welding speed,welding sequence,etc.,thermal stress and deformation can be reduced.
Employing compensation structure design:Rational structural design,such as incorporating symmetric or T-shaped structures,helps reduce welding deformation.
In conclusion,welding deformation is a common issue resulting from thermal stresses and shrinkage during the welding process.The types of welding deformation include buckling,twisting,tensile,compressive,and thickness variation.To control welding deformation,various methods can be employed,such as optimizing welding sequences,using preheating and post-heating treatments,employing suitable fixtures and supports,controlling welding energy input,using appropriate welding methods,applying compensation.
